Fast all-optical switch

Abstract

An apparatus and method wherein polarization rotation in alkali vapors or other mediums is used for all-optical switching and digital logic and where the rate of operation is proportional to the amplitude of the pump field. High rates of speed are accomplished by Rabi flopping of the atomic states using a continuously operating monochromatic atomic beam as the pump.

What is claimed is:  
     
       1. An all-optical switch comprising: 
       an incident optical signal;  
       an optically active polarization rotation medium;  
       an optical pump to produce a stimulated emission and to induce Rabi flopping of the atomic states within said polarization rotation medium; and  
       a polarizing beam splitter.  
     
     
       2. The switch of claim  1  wherein said optical pump comprises a continuous wave optical pump to continuously stimulate said polarization rotation medium. 
     
     
       3. The switch of claim  1  wherein said optical pump comprises a circularly polarized optical pump to create time-dependent circular birefringence within said polarization rotation medium. 
     
     
       4. The switch of claim  1  further comprising a wavelength selective coupler between said polarization rotation medium and said polarizing beam splitter. 
     
     
       5. The switch of claim  1  wherein said polarization rotation medium comprises a medium selected from the group consisting of an optically active vapor and a solid state medium. 
     
     
       6. The switch of claim  5  wherein said optically active vapor comprises an alkali vapor. 
     
     
       7. The switch of claim  1  wherein said incident optical signal comprises a linearly polarized incident optical signal having a right hand circularly polarized component and a left hand circularly polarized component. 
     
     
       8. The switch of claim  7  wherein said polarization rotation medium has a path length such that said right hand circularly polarized component and said left hand circularly polarized component experience different indices of refraction within said polarization rotation medium. 
     
     
       9. The switch of claim  8  wherein said path length is such that said right hand circularly polarized component and said left hand circularly polarized component experience different indices of refraction within said polarization rotation medium such that they become separated by approximately 180 degrees. 
     
     
       10. The switch of claim  1  wherein said switch is used to effectuate an application selected from the group consisting of multiplexing, demultiplexing, all-optical modulation, frequency shift-keying, and digital logic. 
     
     
       11. The switch of claim  1  wherein said polarization rotation medium comprises a solid state medium and said optical pump comprises a linearly polarized optical pump to produce linear birefringence within said solid state medium. 
     
     
       12. The switch of claim  11  wherein said incident optical signal comprises a linearly polarized incident optical signal. 
     
     
       13. The switch of claim  12  wherein said linearly polarized incident optical signal is polarized at approximately 45 degrees relative to said linearly polarized optical pump. 
     
     
       14. The switch of claim  13  wherein said solid state medium has a path length such that approximately 90 degrees of polarization rotation is provided to said incident optical signal. 
     
     
       15. An all-optical switch comprising: 
       an incident optical signal;  
       an optically active polarization rotation medium;  
       a circularly polarized optical pump to produce a stimulated emission and to create time-dependent circular birefringence within said polarization rotation medium; and  
       a polarizing beam splitter.  
     
     
       16. The switch of claim  15  wherein said optical pump comprises a continuous wave optical pump to continuously stimulate said polarization rotation medium. 
     
     
       17. The switch of claim  15  further comprising a wavelength selective coupler between said polarization rotation medium and said polarizing beam splitter. 
     
     
       18. The switch of claim  15  wherein said polarization rotation medium comprises a medium selected from the group consisting of an optically active vapor and a solid state medium. 
     
     
       19. The switch of claim  18  wherein said optically active vapor comprises an alkali vapor. 
     
     
       20. The switch of claim  15  wherein said incident optical signal comprises a linearly polarized incident optical signal having a right hand circularly polarized component and a left hand circularly polarized component. 
     
     
       21. The switch of claim  20  wherein said polarization rotation medium has a path length such that said right hand circularly polarized component and said left hand circularly polarized component experience different indices of refraction within said polarization rotation medium. 
     
     
       22. The switch of claim  21  wherein said path length is such that said right hand circularly polarized component and said left hand circularly polarized component experience different indices of refraction within said polarization rotation medium such that they become separated by approximately 180 degrees. 
     
     
       23. The switch of claim  15  wherein said switch is used to effectuate an application selected from the group consisting of multiplexing, demultiplexing, all-optical modulation, frequency shift-keying, and digital logic. 
     
     
       24. An all-optical switch comprising: 
       an incident optical signal;  
       an optically active polarization rotation medium;  
       an optical pump to produce a stimulated emission within said polarization rotation medium;  
       a polarizing beam splitter; and  
       a wavelength selective coupler between said polarization rotation medium and said polarizing beam splitter.  
     
     
       25. An all-optical switch comprising: 
       an incident optical signal;  
       an optically active polarization rotation medium selected from the group consisting of an optically active vapor and a solid state medium;  
       an optical pump to produce a stimulated emission within said polarization rotation medium; and  
       a polarizing beam splitter.  
     
     
       26. The switch of claim  25  wherein said optical pump comprises a continuous wave optical pump to continuously stimulate said polarization rotation medium. 
     
     
       27. The switch of claim  25  further comprising a wavelength selective coupler between said polarization rotation medium and said polarizing beam splitter. 
     
     
       28. The switch of claim  25  wherein said optically active vapor comprises an alkali vapor. 
     
     
       29. The switch of claim  25  wherein said incident optical signal comprises a linearly polarized incident optical signal having a right hand circularly polarized component and a left hand circularly polarized component. 
     
     
       30. The switch of claim  29  wherein said polarization rotation medium has a path length such that said right hand circularly polarized component and said left hand circularly polarized component experience different indices of refraction within said polarization rotation medium. 
     
     
       31. The switch of claim  30  wherein said path length is such that said right hand circularly polarized component and said left hand circularly polarized component experience different indices of refraction within said polarization rotation medium such that they become separated by approximately 180 degrees. 
     
     
       32. The switch of claim  25  wherein said switch is used to effectuate an application selected from the group consisting of multiplexing, demultiplexing, all-optical modulation, frequency shift-keying, and digital logic. 
     
     
       33. The switch of claim  25  wherein said polarization rotation medium comprises a solid state medium and said optical pump comprises a linearly polarized optical pump to produce linear birefringence within said solid state medium. 
     
     
       34. The switch of claim  33  wherein said incident optical signal comprises a linearly polarized incident optical signal. 
     
     
       35. The switch of claim  34  wherein said linearly polarized incident optical signal is polarized at approximately 45 degrees relative to said linearly polarized optical pump. 
     
     
       36. The switch of claim  35  wherein said solid state medium has a path length such that approximately 90 degrees of polarization rotation is provided to said incident optical signal. 
     
     
       37. An all-optical switch comprising: 
       an incident optical signal;  
       an optically active alkali vapor polarization rotation medium;  
       an optical pump to produce a stimulated emission within said polarization rotation medium; and  
       a polarizing beam splitter.  
     
     
       38. An all-optical switch comprising: 
       a linearly polarized incident optical signal having a right hand circularly polarized component and a left hand circularly polarized component;  
       an optically active polarization rotation medium;  
       an optical pump to produce a stimulated emission within said polarization rotation medium; and  
       a polarizing beam splitter.  
     
     
       39. The switch of claim  38  wherein said optical pump comprises a continuous wave optical pump to continuously stimulate said polarization rotation medium. 
     
     
       40. The switch of claim  38  further comprising a wavelength selective coupler between said polarization rotation medium and said polarizing beam splitter. 
     
     
       41. The switch of claim  38  wherein said polarization rotation medium comprises an optically active alkali vapor. 
     
     
       42. The switch of claim  38  wherein said polarization rotation medium has a path length such that said right hand circularly polarized component and said left hand circularly polarized component experience different indices of refraction within said polarization rotation medium. 
     
     
       43. The switch of claim  42  wherein said path length is such that said right hand circularly polarized component and said left hand circularly polarized component experience different indices of refraction within said polarization rotation medium such that they become separated by approximately 180 degrees. 
     
     
       44. The switch of claim  38  wherein said switch is used to effectuate an application selected from the group consisting of multiplexing, demultiplexing, all-optical modulation, frequency shift-keying, and digital logic. 
     
     
       45. The switch of claim  38  wherein said polarization rotation medium comprises a solid state medium and said optical pump comprises a linearly polarized optical pump to produce linear birefringence within said solid state medium. 
     
     
       46. The switch of claim  45  wherein said linearly polarized incident optical signal is polarized at approximately 45 degrees relative to said linearly polarized optical pump. 
     
     
       47. The switch of claim  46  wherein said solid state medium has a path length such that approximately 90 degrees of polarization rotation is provided to said incident optical signal. 
     
     
       48. An all-optical switch comprising: 
       a linearly polarized incident optical signal having a right hand circularly polarized component and a left hand circularly polarized component;  
       an optically active polarization rotation medium having a path length such that said right hand circularly polarized component and said left hand circularly polarized component experience different indices of refraction within said polarization rotation medium;  
       an optical pump to produce a stimulated emission within said polarization rotation medium; and  
       a polarizing beam splitter.  
     
     
       49. An all-optical switch comprising: 
       a linearly polarized incident optical signal having a right hand circularly polarized component and a left hand circularly polarized component;  
       an optically active polarization rotation medium having a path length such that said right hand circularly polarized component and said left hand circularly polarized component experience different indices of refraction within said polarization rotation medium such that they become separated by approximately 180 degrees;  
       an optical pump to produce a stimulated emission within said polarization rotation medium; and  
       a polarizing beam splitter.  
     
     
       50. An all-optical switch comprising: 
       an incident optical signal;  
       an optically active polarization rotation medium;  
       an optical pump to produce a stimulated emission within said polarization rotation medium; and  
       a polarizing beam splitter,  
       wherein said switch is used to effectuate an application selected from the group consisting of multiplexing, demultiplexing, all-optical modulation, frequency shift-keying, and digital logic.  
     
     
       51. An all-optical switch comprising: 
       an incident optical signal;  
       an optically active solid state polarization rotation medium;  
       a linearly polarized optical pump to produce a stimulated emission within said polarization rotation medium and to produce linear birefringence within said polarization rotation medium; and  
       a polarizing beam splitter.  
     
     
       52. An all-optical switch comprising: 
       linearly polarized incident optical signal;  
       an optically active solid state polarization rotation medium;  
       a linearly polarized optical pump to produce a stimulated emission within said polarization rotation medium and to produce linear birefringence within said solid state medium; and  
       a polarizing beam splitter.  
     
     
       53. An all-optical switch comprising: 
       linearly polarized incident optical signal;  
       an optically active solid state polarization rotation medium;  
       a linearly polarized optical pump to produce a stimulated emission within said polarization rotation medium and to produce linear birefringence within said polarization rotation medium; and  
       a polarizing beam splitter,  
       wherein said linearly polarized incident optical signal is polarized at approximately 45 degrees relative to said linearly polarized optical pump.  
     
     
       54. An all-optical switch comprising: 
       linearly polarized incident optical signal;  
       an optically active solid state polarization rotation medium having a path length such that approximately 90 degrees of polarization rotation is provided to said incident optical signal;  
       a linearly polarized optical pump to produce a stimulated emission within said polarization rotation medium and to produce linear birefringence within said polarization rotation medium; and  
       a polarizing beam splitter,  
       wherein said linearly polarized incident optical signal is polarized at approximately 45 degrees relative to said linearly polarized optical pump.  
     
     
       55. A method of providing all-optical switching, the method comprising the steps of: 
       a) providing an optical signal;  
       b) passing the optical signal through an optically active polarization rotation medium;  
       c) stimulating emission within the polarization rotation medium by pumping with an optical pump and inducing Rabi flopping of the atomic states; and  
       d) splitting the components of the optical signal with a polarizing beam splitter after having passed through the polarization rotation medium.  
     
     
       56. The method of claim  55  wherein the stimulating emission step comprises continuously pumping to continuously stimulate said polarization rotation medium. 
     
     
       57. The method of claim  55  further comprising the step of creating time-dependent circular birefringence within the polarization rotation medium with a circularly polarized optical pump. 
     
     
       58. The method of claim  55  further comprising the step of coupling the optical signal coming out of the polarization rotation medium with the polarizing beam splitter using a wavelength selective coupler. 
     
     
       59. The method of claim  55  wherein the step of passing the optical signal through an optically active polarization rotation medium comprises passing the optical signal through a medium selected from the group consisting of an optically active vapor and a solid state medium. 
     
     
       60. The method of claim  59  wherein the step of passing the optical signal through an optically active vapor comprises passing the optical signal through an alkali vapor. 
     
     
       61. The method of claim  55  wherein the step of providing an optical signal comprises providing a linearly polarized optical signal having a right hand circularly polarized component and a left hand circularly polarized component. 
     
     
       62. The method of claim  61  wherein the step of passing the optical signal through an optically active polarization rotation medium comprises providing a path length such that the right hand circularly polarized component and left hand circularly polarized component of the optical signal experience different indices of refraction within the polarization rotation medium. 
     
     
       63. The method of claim  62  wherein the step of providing a path length such that different indices of refraction are experienced by the two components comprises separating the right hand circularly polarized component and left hand circularly polarized component of the optical signal by approximately 180 degrees. 
     
     
       64. The method of claim  55  further comprising at least one of the steps selected from the group consisting of multiplexing the optical signal, demultiplexing the optical signal, modulating the optical signal, frequency shift-keying the optical signal, and digital logic gating the optical signal. 
     
     
       65. The method of claim  55  wherein the step of passing the optical signal through an optically active polarization rotation medium comprises passing the optical signal through an optically active solid state medium and further comprising the step of creating linear birefringence within the solid state medium with a linearly polarized optical pump. 
     
     
       66. The method of claim  65  wherein the step of providing an optical signal comprises providing a linearly polarized optical signal. 
     
     
       67. The method of claim  66  wherein the step of providing a linearly polarized optical signal comprises providing a linearly polarized optical signal that is polarized at approximately 45 degrees relative to the linearly polarized optical pump. 
     
     
       68. The method of claim  67  wherein the step of passing the optical signal through a solid state medium comprises providing a path length such that approximately 90 degrees of polarization rotation is provided to the optical signal. 
     
     
       69. A method of providing all optical switching, the method comprising the steps of: 
       a) providing an optical signal;  
       b) passing the optical signal through an optically active polarization rotation medium;  
       c) continuously stimulating emission within the polarization rotation medium by continuously pumping with an optical pump; and  
       d) splitting the components of the optical signal with a polarizing beam splitter after having passed through the polarization rotation medium.  
     
     
       70. The method of claim  69  further comprising the step of creating time-dependent circular birefringence within the polarization rotation medium with a circularly polarized optical pump. 
     
     
       71. The method of claim  69  further comprising the step of coupling the optical signal coming out of the polarization rotation medium with the polarizing beam splitter using a wavelength selective coupler. 
     
     
       72. The method of claim  69  wherein the step of passing the optical signal through an optically active polarization rotation medium comprises passing the optical signal through a medium selected from the group consisting of an optically active vapor and a solid state medium. 
     
     
       73. The method of claim  72  wherein the step of passing the optical signal through an optically active vapor comprises passing the optical signal through an alkali vapor. 
     
     
       74. The method of claim  69  wherein the step of providing an optical signal comprises providing a linearly polarized optical signal having a right hand circularly polarized component and a left hand circularly polarized component. 
     
     
       75. The method of claim  74  wherein the step of passing the optical signal through an optically active polarization rotation medium comprises providing a path length such that the right hand circularly polarized component and left hand circularly polarized component of the optical signal experience different indices of refraction within the polarization rotation medium. 
     
     
       76. The method of claim  75  wherein the step of providing a path length such that different indices of refraction are experienced by the two components comprises separating the right hand circularly polarized component and left hand circularly polarized component of the optical signal by approximately 180 degrees. 
     
     
       77. The method of claim  69  further comprising at least one of the steps selected from the group consisting of multiplexing the optical signal, demultiplexing the optical signal, modulating the optical signal, frequency shift-keying the optical signal, and digital logic gating the optical signal. 
     
     
       78. The method of claim  69  wherein the step of passing the optical signal through an optically active polarization rotation medium comprises passing the optical signal through an optically active solid state medium and further comprising the step of creating linear birefringence within the solid state medium with a linearly polarized optical pump. 
     
     
       79. The method of claim  78  wherein the step of providing an optical signal comprises providing a linearly polarized optical signal. 
     
     
       80. The method of claim  79  wherein the step of providing a linearly polarized optical signal comprises providing a linearly polarized optical signal that is polarized at approximately 45 degrees relative to the linearly polarized optical pump. 
     
     
       81. The method of claim  80  wherein the step of passing the optical signal through a solid state medium comprises providing a path length such that approximately 90 degrees of polarization rotation is provided to the optical signal. 
     
     
       82. A method of providing all-optical switching, the method comprising the steps of: 
       a) providing an optical signal;  
       b) passing the optical signal through an optically active polarization rotation medium;  
       c) stimulating emission and creating time-dependent circular birefringence within the polarization rotation medium by pumping with a circularly polarized optical pump; and  
       d) splitting the components of the optical signal with a polarizing beam splitter after having passed through the polarization rotation medium.  
     
     
       83. The method of claim  82  further comprising the step of coupling the optical signal coming out of the polarization rotation medium with the polarizing beam splitter using a wavelength selective coupler. 
     
     
       84. The method of claim  82  wherein the step of passing the optical signal through an optically active polarization rotation medium comprises passing the optical signal through a medium selected from the group consisting of an optically active vapor and a solid state medium. 
     
     
       85. The method of claim  84  wherein the step of passing the optical signal through an optically active vapor comprises passing the optical signal through an alkali vapor. 
     
     
       86. The method of claim  82  wherein the step of providing an optical signal comprises providing a linearly polarized optical signal having a right hand circularly polarized component and a left hand circularly polarized component. 
     
     
       87. The method of claim  86  wherein the step of passing the optical signal through an optically active polarization rotation medium comprises providing a path length such that the right hand circularly polarized component and left hand circularly polarized component of the optical signal experience different indices of refraction within the polarization rotation medium. 
     
     
       88. The method of claim  87  wherein the step of providing a path length such that different indices of refraction are experienced by the two components comprises separating the right hand circularly polarized component and left hand circularly polarized component of the optical signal by approximately 180 degrees. 
     
     
       89. The method of claim  82  further comprising at least one of the steps selected from the group consisting of multiplexing the optical signal, demultiplexing the optical signal, modulating the optical signal, frequency shift-keying the optical signal, and digital logic gating the optical signal. 
     
     
       90. A method of providing all-optical switching, the method comprising the steps of: 
       a) providing an optical signal;  
       b) passing the optical signal through an optically active polarization rotation medium;  
       c) stimulating emission within the polarization rotation medium by pumping with an optical pump;  
       d) splitting the components of the optical signal with a polarizing beam splitter after having passed through the polarization rotation medium; and  
       e) coupling the optical signal coming out of the polarization rotation medium with the polarizing beam splitter using a wavelength selective coupler.  
     
     
       91. A method of providing all-optical switching, the method comprising the steps of: 
       a) providing an optical signal;  
       b) passing the optical signal through an optically active polarization rotation medium selected from the group consisting of an optically active vapor and a solid state medium;  
       c) stimulating emission within the polarization rotation medium by pumping with an optical pump; and  
       d) splitting the components of the optical signal with a polarizing beam splitter after having passed through the polarization rotation medium.  
     
     
       92. The method of claim  91  further comprising the step of coupling the optical signal coming out of the polarization rotation medium with the polarizing beam splitter using a wavelength selective coupler. 
     
     
       93. The method of claim  91  wherein the step of passing the optical signal through an optically active vapor comprises passing the optical signal through an alkali vapor. 
     
     
       94. The method of claim  91  wherein the step of providing an optical signal comprises providing a linearly polarized optical signal having a right hand circularly polarized component and a left hand circularly polarized component. 
     
     
       95. The method of claim  94  wherein the step of passing the optical signal through an optically active polarization rotation medium comprises providing a path length such that the right hand circularly polarized component and left hand circularly polarized component of the optical signal experience different indices of refraction within the polarization rotation medium. 
     
     
       96. The method of claim  95  wherein the step of providing a path length such that different indices of refraction are experienced by the two components comprises separating the right hand circularly polarized component and left hand circularly polarized component of the optical signal by approximately 180 degrees. 
     
     
       97. The method of claim  91  further comprising at least one of the steps selected from the group consisting of multiplexing the optical signal, demultiplexing the optical signal, modulating the optical signal, frequency shift-keying the optical signal, and digital logic gating the optical signal. 
     
     
       98. The method of claim  91  wherein the step of passing the optical signal through an optically active polarization rotation medium comprises passing the optical signal through an optically active solid state medium and further comprising the step of creating linear birefringence within the solid state medium with a linearly polarized optical pump. 
     
     
       99. The method of claim  98  wherein the step of providing an optical signal comprises providing a linearly polarized optical signal. 
     
     
       100. The method of claim  99  wherein the step of providing a linearly polarized optical signal comprises providing a linearly polarized optical signal that is polarized at approximately 45 degrees relative to the linearly polarized optical pump. 
     
     
       101. The method of claim  100  wherein the step of passing the optical signal through a solid state medium comprises providing a path length such that approximately 90 degrees of polarization rotation is provided to the optical signal. 
     
     
       102. A method of providing all-optical switching, the method comprising the steps of: 
       a) providing an optical signal;  
       b) passing the optical signal through an optically active alkali vapor polarization rotation medium;  
       c) stimulating emission within the polarization rotation medium by pumping with an optical pump; and  
       d) splitting the components of the optical signal with a polarizing beam splitter after having passed through the polarization rotation medium.  
     
     
       103. A method of providing all-optical switching, the method comprising the steps of: 
       a) providing a linearly polarized optical signal having a right hand circularly polarized component and a left hand circularly polarized component;  
       b) passing the optical signal through an optically active polarization rotation medium;  
       c) stimulating emission within the polarization rotation medium by pumping with an optical pump; and  
       d) splitting the components of the optical signal with a polarizing beam splitter after having passed through the polarization rotation medium.  
     
     
       104. The method of claim  103  further comprising the step of coupling the optical signal coming out of the polarization rotation medium with the polarizing beam splitter using a wavelength selective coupler. 
     
     
       105. The method of claim  103  wherein the step of passing the optical signal through an optically active polarization rotation medium comprises passing the optical signal through an optically active alkali vapor. 
     
     
       106. The method of claim  103  wherein the step of passing the optical signal through an optically active polarization rotation medium comprises providing a path length such that the right hand circularly polarized component and left hand circularly polarized component of the optical signal experience different indices of refraction within the polarization rotation medium. 
     
     
       107. The method of claim  106  wherein the step of providing a path length such that different indices of refraction are experienced by the two components comprises separating the right hand circularly polarized component and left hand circularly polarized component of the optical signal by approximately 180 degrees. 
     
     
       108. The method of claim  103  further comprising at least one of the steps selected from the group consisting of multiplexing the optical signal, demultiplexing the optical signal, modulating the optical signal, frequency shift-keying the optical signal, and digital logic gating the optical signal. 
     
     
       109. The method of claim  103  wherein the step of passing the optical signal through an optically active polarization rotation medium comprises passing the optical signal through an optically active solid state medium and further comprising the step of creating linear birefringence within the solid state medium with a linearly polarized optical pump. 
     
     
       110. The method of claim  109  wherein the step of providing a linearly polarized optical signal comprises providing a linearly polarized optical signal that is polarized at approximately 45 degrees relative to the linearly polarized optical pump. 
     
     
       111. The method of claim  110  wherein the step of passing the optical signal through a solid state medium comprises providing a path length such that approximately 90 degrees of polarization rotation is provided to the optical signal. 
     
     
       112. A method of providing all-optical switching, the method comprising the steps of: 
       a) providing a linearly polarized optical signal having a right hand circularly polarized component and a left hand circularly polarized component;  
       b) passing the optical signal through an optically active polarization rotation medium and providing a path length such that the right hand circularly polarized component and left hand circularly polarized component of the optical signal experience different indices of refraction within the polarization rotation medium;  
       c) stimulating emission within the polarization rotation medium by pumping with an optical pump; and  
       d) splitting the components of the optical signal with a polarizing beam splitter after having passed through the polarization rotation medium.  
     
     
       113. A method of providing all optical switching, the method comprising the steps of: 
       a) providing a linearly polarized optical signal having a right hand circularly polarized component and a left hand circularly polarized component;  
       b) passing the optical signal through an optically active polarization rotation medium and providing a path length such that the right hand circularly polarized component and left hand circularly polarized component of the optical signal experience different indices of refraction within the polarization rotation medium and are separated by approximately 180 degrees;  
       c) stimulating emission within the polarization rotation medium by pumping with an optical pump; and  
       d) splitting the components of the optical signal with a polarizing beam splitter after having passed through the polarization rotation medium.  
     
     
       114. A method of providing all-optical switching, the method comprising the steps of: 
       a) providing an optical signal;  
       b) passing the optical signal through an optically active polarization rotation medium;  
       c) stimulating emission within the polarization rotation medium by pumping with an optical pump;  
       d) splitting the components of the optical signal with a polarizing beam splitter after having passed through the polarization rotation medium; and  
       e) at least one of the steps selected from the group consisting of multiplexing the optical signal, demultiplexing the optical signal, modulating the optical signal, frequency shift-keying the optical signal, and digital logic gating the optical signal.  
     
     
       115. A method of providing all-optical switching, the method comprising the steps of: 
       a) providing an optical signal;  
       b) passing the optical signal through an optically active solid state polarization rotation medium;  
       c) stimulating emission and creating linear birefringence within the solid state medium by pumping with a linearly polarized optical pump; and  
       d) splitting the components of the optical signal with a polarizing beam splitter after having passed through the polarization rotation medium.  
     
     
       116. A method of providing all-optical switching, the method comprising the steps of: 
       a) providing a linearly polarized optical signal;  
       b) passing the optical signal through an optically active solid state polarization rotation medium;  
       c) stimulating emission and creating linear birefringence within the solid state medium by pumping with a linearly polarized optical pump; and  
       d) splitting the components of the optical signal with a polarizing beam splitter after having passed through the polarization rotation medium.  
     
     
       117. A method of providing all-optical switching, the method comprising the steps of: 
       a) providing a linearly polarized optical signal that is polarized at approximately 45 degrees relative to a linearly polarized optical pump;  
       b) passing the optical signal through an optically active solid state polarization rotation medium;  
       c) stimulating emission and creating linear birefringence within the solid state medium by pumping with the linearly polarized optical pump; and  
       d) splitting the components of the optical signal with a polarizing beam splitter after having passed through the polarization rotation medium.  
     
     
       118. A method of providing all-optical switching, the method comprising the steps of: 
       a) providing a linearly polarized optical signal that is polarized at approximately 45 degrees relative to a linearly polarized optical pump;  
       b) passing the optical signal through an optically active solid state polarization rotation medium and providing a path length such that approximately 90 degrees of polarization rotation is provided to the optical signal;  
       c) stimulating emission and creating linear birefringence within the solid state medium by pumping with the linearly polarized optical pump; and  
       d) splitting the components of the optical signal with a polarizing beam splitter after having passed through the polarization rotation medium.